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Metal-enhanced fluorescence of interlaminar composite film with self-assembled quantum Dots/Au@SiO2 microarchitecture
摘要： Quantum dots fluorescence-enhanced films, which mainly consisted of CdSe@ZnS quantum dots and noble metal nanoparticles or nanorods, were formed by layer-by-layer self-assembly techniques. This particular architecture consisting of metal nanoparticles-poly (diallyl dimethylammonium chloride) (PDDA)-QDs was characterized by those fabrication processes mainly including surface-modifying the oleic acid-capped CdSe@ZnS QDs ( high quantum yield of ~89% ) with mercaptopropionic acid (MPA) to be charged negatively (-COO-) for following solution-processed assembly, adjusting the size and coating the gold nanoparticles/nanorods with silica to form suitable dielectric insulation layer and further optimize the fluorescence-enhanced performance, as well as using the cationic polyelectrolyte to control the charges between layers and form opposite charges between two adjacent layers. After optimizing the structure of the quantum dot fluorescence-enhanced films and corresponding surface plasmon enhancement effect, the enhancement factor of 10.8 in Au NPs@SiO2-PDDA-QDs complex film and that of 24.7 in Au NRs@SiO2-PDDA-QDs complex film as compared with the pure quantum dot fluorescence film were achieved, respectively. This indicated that the Au NRs@SiO2-PDDA-QDs complex film was one of the most promising potentials for further display backlight and biometric identifier application.
关键词： CdSe@ZnS quantum dots,Au@SiO2 microarchitecture,electrostatic self-assembly,metal surface plasmon enhancement,Quantum dots fluorescence-enhanced films
更新于2025-09-12 10:27:22
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Three-dimensional ZnO/ZnxCd1?xS/CdS nanostructures modified by microwave hydrothermal reaction-deposited CdSe quantum dots for chemical solar cells
摘要： Effective interfaces composed of smart materials could play a critical role in the rapid transfer and separation of charges to achieve the high power-conversion efficiency of solar cells. In this work, we report an efficient chemical solar cell that uses a ZnO/ZnxCd1?xS/CdS structure, modified with CdSe deposited with a microwave hydrothermal technique, for rapid transport of charges using a frame construction to allow for reuse. The morphology, nanostructure, and reaction mechanisms of CdS nanorods and the ZnxCd1?xS layer were systematically investigated. The results indicated that light absorption expands from 550 nm of CdS to 700 nm because of the absorption of nearly all the visible light by deposited CdSe quantum dots. The effects of the compositional structure on cell performance are investigated to reveal the enhancement mechanism, which is mainly attributed to the suitable nano-branch structure, high light absorbability, low charge transfer resistance, and low recombination rate. This work demonstrates a potential universal method of designing an interface with a multi-component composite for efficient charge transport and separation, not only in chemical solar cells but with extensions to photocatalysis and water splitting uses as well.
关键词： Chemical solar cell,Composite structures,ZnO/ZnxCd1?xS/CdS,CdSe quantum dots,Microwave hydrothermal
更新于2025-09-12 10:27:22
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Growth of CdSe/MoS2 vertical heterostructures for fast visible-wavelength photodetectors
摘要： Heterostructures composed of different semiconducting materials have aroused wide attentions due to their fascinating properties originated from the interfaces. Particularly, the recent two dimensional layered materials (2DLM) have provided novel platforms to flexibly design the heterostructures for diverse electronic and optoelectronic applications. In this work, we have reported the growth of CdSe nanoplates/MoS2 monolayer vertical heterostructures with efficient and fast visible-wavelength photodetections. Highly dense CdSe nanoplates were vertically assembled on monolayer MoS2 through a two-step chemical vapor deposition (CVD) process. The interfacial photoinduced charge behaviors were investigated in detail via the time resolution photoluminescence (TRPL) measurements, revealing the efficient charge transfer across the heterointerface. Benefiting from the large CdSe coverage and efficient charge transfer, superior photodetection performances of the CdSe/MoS2 heterostructures can be obtained with an enhanced photoresponsivity of 1.63 A/W, which can be further improved to be 12 A/W via applying the gate voltage. Besides, the heterostructure detectors also exhibit a very fast photoresponse speed of 370 μs, much faster than previous photodetectors based on CVD-grown 2D heterostructures. The as-synthesized CdSe/MoS2 heterostructures may find important applications in integrated optoelectronic systems.
关键词： Responsivity,Chemical vapor deposition,Photodetectors,Vertical heterostructures,CdSe/MoS2
更新于2025-09-12 10:27:22
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Simultaneous positive and negative optical patterning with dye-sensitized CdSe quantum dots
摘要： CdSe quantum dots are functionalized with the organic dye iron β-tetraaminophthalocyanine to reward a solution-processable hybrid material with two individually addressable optical resonances. We exploit this dual functionality during optical write/optical read patterning experiments and show that it is possible to simultaneously write complex optical patterns with positive and negative fluorescence contrast. This is enabled by a fluorescence enhancement under near-resonant excitation of the quantum dots in combination with a fluorescence bleaching during excitation of the singlet transition of the phthalocyanine. The presence of the organic dye not only enables negative optical patterning but also enhances the contrast during positive patterning. Furthermore, the patterning result is strongly dependent on the excitation wavelength during readout. Our results highlight the new possibilities that arise from combining inorganic quantum dots and organic π-systems into hybrid nanocomposites.
关键词： fluorescence contrast,optical patterning,iron β-tetraaminophthalocyanine,CdSe quantum dots,hybrid nanocomposites
更新于2025-09-12 10:27:22
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Low‐Threshold Amplified Spontaneous Emission and Lasing from Thick‐Shell CdSe/CdS Core/Shell Nanoplatelets Enabled by High‐Temperature Growth
摘要： Colloidal semiconductor nanoplatelets (NPLs) have recently emerged as highly promising optical gain medium because of their superior optical properties. Here, the shell-thickness-dependent optical gain properties of CdSe/CdS core/shell NPLs synthesized by high-temperature growth are systematically investigated for the first time. The core/shell NPLs show the increased quantum yields and enhanced photostability as well as clear reduced emission blinking, thanks to the preferable passivation of nonradiative surface defects by the growth of the high-quality CdS shells under high reaction temperature. Meanwhile, the amplified spontaneous emission (ASE) performance of CdSe/CdS NPLs indicates a nonmonotonic dependence on the shell thickness. The ASE threshold is achieved as low as ≈4.4 μJ cm?2 for thick-shell NPLs with six monolayer CdS shells, and exhibiting ultrafast transient dynamics process (≈11 ps). Besides, an extremely long lifetime (>800 ps) and large bandwidth (>140 nm) of optical gain are observed by employing ultrafast transient absorption spectroscopy. Finally, a thick-shell NPLs vertical cavity surface-emitting laser is developed, which demonstrates spatially directional single-mode operation with an ultralow lasing threshold of ≈1.1 μJ cm?2. These excellent results are attributed to the remarkable optical gain performance of core/shell NPLs and represent an important step toward practical NPL laser devices.
关键词： CdSe/CdS,amplified spontaneous emission,nanoplatelets,vertical cavity surface-emitting laser,optical gain
更新于2025-09-12 10:27:22
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The electronic and optical properties of an exciton, biexciton and charged excitons in CdSe/CdTe-based multi-shell type-II quantum dot nanocrystals
摘要： It has been recently reported that multi-shell type-II quantum dot nanocrystals (QDNCs) have higher quantum yields. Besides these higher quantum yields of multi-shell type-II QDNCs, additional second layer has been a critical influence on the formation mechanisms of the excitonic structures. Understanding of bound and unbound cases of the excitonic structures in multi-shell type-II QDNCs gives some important information for applications. In this study, we have investigated the electronic and optical properties of a single exciton (X), biexciton (XX), and positively and negatively charged excitons ( ??+ and ??? ) in CdSe/CdTe-based multi-shell type-II QDNCs. In the study, three different structure compositions, i.e., CdSe/CdTe, CdSe/CdTe/CdS, and CdSe/CdTe/ZnTe, have been considered. We have observed that CdS and ZnTe materials have drastically changed the electronic and optical properties of the bare CdSe/CdTe type-II QDNCs.
关键词： Exciton,CdS,Biexciton,CdSe/CdTe,Charged excitons,ZnTe,Quantum dot nanocrystals,Type-II
更新于2025-09-12 10:27:22
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Enzyme-Catalyzed in Situ Synthesis of Temporally and Spatially Distinct CdSe Quantum Dots in Biological Backgrounds
摘要： The cellular machinery of metal metabolism is capable of making a wide range of inorganic nanoparticles and quantum dots. Individual enzymes from these metabolic pathways are being identified with metal reducing activity, and some have been isolated for in situ particle formation and labeling. We previously identified a glutathione reductase like metalloid reductase (GRLMR) from Pseudomonas moravenis stanleyae with a high affinity for the bioavailable selenium thiolate selenodiglutatione and exhibiting NADPH-dependent reduction of selenodiglutathione to Se(0), initiating the growth of pure selenium metal nanoparticles. In this study, we demonstrate that the GRLMR enzyme can further reduce selenium to a Se(2?) oxidative state, which is capable of nucleating with Cd(2+) to rapidly form CdSe quantum dots. We show that GRLMR can outcompete background sources of cellular selenium reduction (such as glutathione) and can control the kinetics of quantum dot formation in complex media. The resulting particles are of smaller diameter, with a distinguishingly shifted emission spectrum and superior full width at half-maximum. This study indicates that there is great potential for using GRLMR to study and design enzymes capable of controlled biosynthesis of nanoparticles and quantum dots, paving the way for cellularly assembled nanoparticle biosensors and reporters.
关键词： enzyme-catalyzed,CdSe quantum dots,nanoparticle biosynthesis,GRLMR,biological backgrounds,selenium reduction
更新于2025-09-12 10:27:22
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Bright Cool White Emission from Ultrasmall CdSe Quantum Dots
摘要： In this work we employ a post-synthesis ligand treatment of ultrasmall CdSe quantum dots (QDs) with citric acid to increase the quantum yield (QY) of the of the as-synthesized CdSe from an average of 5.7% to a maximum of 61.3%. This is the highest reported value for a single component white-light emitting QD. The white-light emission of the ultrasmall CdSe quantum dots is derived from three surface states: pinned emission at a trap state associated with the phosphonic acid surface ligand, a surface Se state, and conventional deep trap states. The citric acid treated CdSe QDs were found to recover band gap emission from the phosphonic acid ligand trap state emission, exhibiting behavior . This band gap emission peak also becomes more prominent, resulting in a cooler white, as indicated by the shift in the CIE coordinates from an average of (0.30, 0.36) to (0.26, 0.32). Comparing to a previous method of increasing the QY by a post-synthesis treatment of formic acid, the citric acid treated CdSe QDs are brighter as well as more stable in solution over time, which opens the possibility for use in multiple applications.
关键词： white-light emission,quantum yield,quantum dots,citric acid,CdSe
更新于2025-09-12 10:27:22
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Photoinduced Modulation of the Emission from СdSe/ZnS Quantum Dots by Photochromic Transformations of Diarylethenes
摘要： A spectral study of the interaction between the molecules of photochromic compounds of the diarylethene class and CdSe/ZnS quantum dots (QDs), in dependence of the structure and nature of functional substituents of photochromes, has been performed. It is shown that both chemical and physical interactions are accompanied by photoinduced modulation of QD emission as a result of photochromic transformations of diarylethenes caused by the inductive transfer of excitation energy from QDs to the diarylethene cyclic isomer.
关键词： diarylethenes,CdSe/ZnS quantum dots,nanomaterials,photoinduced modulation,photochromic transformations,ceramics
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Extension of Mid-IR Lasing Spectral Region using Cr:ZnSe and Cr:CdSe Combined Active Medium
摘要： High intensity femtosecond solid-state lasers in mid-infrared (mid-IR) region are of significant interest for many applications such as laser processing, ultrafast spectroscopy, high-order harmonic generation, and laser plasma acceleration. Transition metal (TM) doped chalcogenides (Cr:ZnSe, Cr:CdSe, Fe:ZnSe etc.) are attractive laser media for high intensity mid-IR femtosecond lasers, since they have broad fluorescence spectrum and large stimulated-emission cross section in the mid-IR region [1]. Extension of lasing region by combining of fluorescence region of TM doped chalcogenides can contribute to generate mid-IR ultrashort pulses. Combined active medium method [2-4], by which multiple laser media are used inside a laser cavity simultaneously, is suitable for equipping lasing characteristics of multiple laser media on one laser oscillator. This method has high potential to oscillate ultrashort pulses directly from a solid-state laser, however the method has not been realized in the mid-IR region. In this study, we report on extension of mid-IR lasing region using Cr:ZnSe and Cr:CdSe combined active medium (CAM). We obserbed that wavelength tunability was extended when using Cr:ZnSe and Cr:CdSe CAM than when using Cr:ZnSe and Cr:CdSe indipendently. This is the first report that CAM technique based on Cr2+ doped chalcogenides was demonstrated in the mid-IR region.
关键词： Cr:CdSe,femtosecond lasers,combined active medium,mid-IR lasing,Cr:ZnSe
更新于2025-09-12 10:27:22